EJ&E Baldwin Centercab Part 2: Chassis and DCC

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The 3D printed centercab shell was designed to fit over a Stewart Alco C-628 or C-630 chassis. I found a second-hand C-628 that ran smoothly out of the box. The engine rides on Alco Trimount trucks, which needed to be swapped out for the Commonwealth trucks used under the Baldwin centercabs. Like the Commonwealth trucks, the Alco trucks have an offset axle spacing. However, the direction of the offset (short spacing towards the coupler side) is reversed compared to the centercab trucks (long spacing towards the coupler side).


Following instructions on the James Model Railways website, I purchased his set of replacement gear towers and gears from Shapeways that included the correct axle offset. I also purchased the correct Commonwealth side frames directly from Bowser. The side frame kit also came with improved electrical pickups to draw power from all three axles in the truck instead of just two, as on the older Stewart model.




Unfortunately, the 3D printed gear towers were simply too brittle to hold up to the mechanical stresses of functional drive train components. I broke off some of the friction-fit pegs right off the bat and ran into problems with the 3D printed gears binding up. Pursuing this solution seemed to be setting myself up for future operational headaches, so I decided to keep the original Stewart gear towers and simply swap the Alco side frames for the Commonwealth ones. This resulted in a much smoother and more reliable mechanism at the expense of keeping the incorrect axle offset.


I scrapped the original Stewart light board and wired in a Soundtraxx Tsunami2 diesel decoder that fit above the motor in a similar footprint. I used golden-white LEDs for the headlights on each end. A rectangular Tang Band speaker fit nicely in one end of the hood and a Soundtraxx Current Keeper in the other end. The inside of the shell is just barely wide enough to fit over the decoder and motor. I had to take care that any wires attached to the side of the board (motor leads & lighting functions) did not extend past the footprint of the board itself.




I had lubricated and tested the mechanism before decoder installation and continued to test it as I finished the wiring. This resulted in a smooth and quietly running chassis. In parallel, I painted the shell before the final headlight and speaker installation, and paint will be the subject of part 3. Couldn’t resist taking the mostly completed engine for a spin on the club layout:




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